Abstract:Six lactic acid bacterial (LAB) strains were isolated from traditionally fermented Xinjiang cheese and evaluated for functional and probiotic properties and potentials as starter cultures. The isolated six LAB strains comprised Lactobacillus rhamnosus (one strain), Lactobacillus helveticus (one strain), and Enterococcus hirae (four strains). All of the six strains were tolerant to acidic and bile salt conditions. Among which, the L. rhamnosus R4 strain showed more desirable antimicrobial, auto-aggregation, and hydrophobic activity. In addition, the strain L. rhamnosus R4 exhibited the highest level of free radical scavenging activity (53.78% of 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals and 45.79% of hydroxyl radicals). L. rhamnosus R4 also demonstrated cholesterol and triglyceride degradation by 50.97% and 28.92%, respectively. To further examine the health-promoting effects of these LAB strains on host lifespan, Caenorhabditis elegans was used as an in vivo model. Worms fed LAB as a food source had significant differences in lifespan compared to those fed Escherichia coli OP50 (as a negative control). Feeding of L. rhamnosus R4 extended the mean lifespan of C. elegans by up to 36.1% compared to that of the control. The results suggest that the strains isolated from Xinjiang fermented dairy products have high potential as starter cultures in the cheese industry.

Mulberry anthocyanins possess many pharmacological effects including liver protection, anti-inflammation, and anticancer. The aim of this study was to evaluate whether mulberry anthocyanin extract (MAE) exerts beneficial effects against oxidative stress damage in HepG2 cells and Caenorhabditis elegans. In vitro, MAE prevented cytotoxicity, increased glucose consumption and uptake, and eliminated excessive intracellular free radicals in H2O2-induced cells. Moreover, MAE pretreatment maintained Nrf2, HO-1, and p38 MAPK stimulation and abolished upregulation of p-JNK, FOXO1, and PGC-1α that were involved in oxidative stress and insulin signalling modulation. In vivo, extended lifespan was observed in C. elegans damaged by paraquat in the presence of MAE, while these beneficial effects were disappeared in pmk-1 and daf-16 mutants. PMK-1 and SKN-1 were activated after exposure to paraquat and MAE suppressed PMK-1 activation but enhanced SKN-1 stimulation. Our findings suggested that MAE recovered redox status in HepG2 cells and C. elegans that suffered from oxidative stress, which might be by targeting MAPKs and Nrf2.

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Validamycin A (Val-A) synthesized by Streptomyces hygroscopicus 5008 is widely used as a high-efficient antibiotic to protect plants from sheath blight disease. A novel fermentation strategy was introduced to stimulate Val-A production by adding oxygen carriers. About 58 % increase in Val-A production was achieved using liquid paraffin. Further, biomass, carbon source, metabolic genes, and metabolic enzymes were studied. It was also found that the supplementation of liquid paraffin increased the medium dissolved oxygen and intracellular oxidative stress level. The expression of the global regulators afsR and soxR sensitive to ROS, ugp catalyzing synthesis of Val-A precursor, and Val-A structural genes was enhanced. The change of the activities of glucose-6-phosphate dehydrogenase and glyceraldehyde 3-phosphate dehydrogenase was observed, which reflected the redirection of carbon metabolic flux. Based on these results, liquid paraffin addition as an oxygen carrier could be a useful technique in industrial production of Val-A and our study revealed a redox-based secondary metabolic regulation in S. hygroscopicus 5008, which provided a new insight into the regulation of the biosynthesis of secondary metabolites.